Quantum-induced solid-solid transitions and melting in the Lennard-Jones LJ38 cluster.

The solid-solid and melting transitions that occur in Lennard-Jones LJ n clusters have been both fascinating and challenging for the computational physics community over the last several decades. A number of attempts to extend these studies to the quantum case have also been made. Particularly interesting is the exploration of the parallel between the thermally induced and quantum-induced transitions. Yet, both numerically accurate and systematic studies of the latter are still lacking. In this paper, we apply the diffusion Monte Carlo method to the especially difficult case of LJ38. Starting with the truncated octahedral global minimum configuration, as the de Boer quantum delocalization parameter Λ increases, the system undergoes two consecutive solid-solid transitions, switching to anti-Mackay configurations. At sufficiently large values of Λ, the cluster is completely "melted," which is manifested by delocalization of the ground state wavefunction over a very large number of minima that represent several structural motifs.